JP6676896B2

JP6676896B2 - Method for producing undrawn polypropylene yarn and method for producing polypropylene fiber

Info

Publication number: JP6676896B2
Application number: JP2015146904A
Authority: JP
Inventors: 正樹藤江; 山下　友義; 友義山下; 裕信池田; 純哉今北
Original assignee: Mitsubishi Chemical Corp
Current assignee: Mitsubishi Chemical Corp
Priority date: 2015-07-24
Filing date: 2015-07-24
Publication date: 2020-04-08
Anticipated expiration: 2035-07-24
Also published as: JP2017025449A

Description

本発明は、産業資材用、建造物や自動車などの内装用、医療・衛生用、衣料用などに用いられるポリプロピレン繊維の未延伸糸の製造方法及びその製造方法から得られる未延伸糸から得られるポリプロピレン繊維の製造方法に関する。 The present invention, industrial materials, buildings and for interiors such as automotive, medical and hygiene, undrawn yarn or we obtained resulting from the manufacturing method and the manufacturing method thereof of the undrawn yarn of polypropylene fibers used in such clothing And a method for producing a polypropylene fiber.

ポリプロピレン繊維は撥水性、非吸収性に優れ、低比重であるため軽くて、また耐薬品性に優れているなどの特性を有していることから、産業資材用、建造物や自動車などの内装用、医療・衛生用、衣料用などに広く用いられている。特に産業資材用途では軽さと強度を活かしてロープ、養生ネット、水平ネットなど幅広く用いられているが、更なる高強度化が求められている。 Polypropylene fiber has properties such as excellent water repellency, non-absorbency, low specific gravity, light weight, and excellent chemical resistance, so it is used for industrial materials, interior of buildings and automobiles. It is widely used for medical, hygiene and clothing purposes. Particularly in industrial materials, ropes, curing nets, horizontal nets, and the like are widely used by taking advantage of their lightness and strength, but further higher strength is required.

ポリプロピレン繊維の強度は延伸条件に大きく依存することが知られている。特に延伸倍率を高くするとポリプロピレン繊維の強度は大きく向上する。しかし、通常の延伸速度で高倍率に延伸しようとすると毛羽・糸切れが頻発してしまうため安定的に生産するのが難しくなる。そこで延伸速度を遅くして可能な限り高倍率で延伸することで高強度化する試みがなされている。 It is known that the strength of a polypropylene fiber largely depends on drawing conditions. In particular, when the draw ratio is increased, the strength of the polypropylene fiber is greatly improved. However, if the film is stretched at a high magnification at a normal stretching speed, fluff and yarn breakage occur frequently, so that it is difficult to stably produce the film. Attempts have been made to increase the strength by slowing the stretching speed and stretching at the highest possible magnification.

例えば、国際公開第２０１２／１６４６５６号（特許文献１）ではポリプロピレンを溶融押出して、ポリプロピレンのガラス転移温度以上でかつガラス転移温度＋１５℃以下の温度に急冷する紡糸工程と、該温度で保冷する保冷工程と、延伸工程とを含むポリプロピレン繊維の製造方法について提案されている。この方法では１．６ＧＰａ以上の高強度になると記載されているが、延伸は手回し延伸機で極めて低速度で延伸しており、更に０℃で数日間保冷するなど工業的には実施が難しいと考えられる。 For example, in WO2012 / 164656 (Patent Document 1), a spinning step in which polypropylene is melt-extruded and rapidly cooled to a temperature equal to or higher than the glass transition temperature of polypropylene and equal to or lower than the glass transition temperature + 15 ° C. A method for producing a polypropylene fiber including a step and a drawing step has been proposed. Although it is described that this method has a high strength of 1.6 GPa or more, stretching is performed at an extremely low speed with a hand-drawn stretching machine, and it is difficult to implement industrially such as keeping it cool at 0 ° C. for several days. Conceivable.

また、例えば特開２００３−２９３２１６号公報（特許文献２）では、繊維表面の曲面に沿って形成された筋状の粗面構造を有する、単糸強度が９ｃＮ／ｄｔｅｘのコンクリート補強用のポリプロピレン繊維が提案されている。しかし、これも延伸速度は５０ｍ／分程度の速度で行っており生産性に劣る。 Also, for example, in JP-A-2003-293216 (Patent Document 2), a polypropylene fiber for concrete reinforcement having a streak-like rough surface structure formed along a curved surface of a fiber surface and having a single yarn strength of 9 cN / dtex is disclosed. Has been proposed. However, this is also performed at a stretching speed of about 50 m / min, which is inferior in productivity.

更に、例えばまた特開２００２−１８０３４７号公報（特許文献３）では両端が加圧水でシールされた容器内に、延伸媒体として０．３〜０．５ＭＰａ程度の加圧飽和水蒸気が充填されてなる延伸槽を用いて、結晶性高分子物質を延伸処理する方法について記載されている。この手法では９．７ｃＮ／ｄｔｅｘ以上の高強度ポリプロピレン繊維の製造が可能である。しかし、この手法では通常の熱板延伸などに比べて、特殊で高価な加圧飽和水蒸気延伸装置が必要であり、更に加圧飽和水蒸気延伸では繊維の投入量が制限されてしまう問題があるため、大量生産には不向きである。 Further, for example, Japanese Patent Application Laid-Open No. 2002-180347 (Patent Document 3) discloses that a container sealed at both ends with pressurized water is filled with saturated steam under pressure of about 0.3 to 0.5 MPa as a stretching medium. A method for stretching a crystalline polymer material using a bath is described. With this method, it is possible to produce a high-strength polypropylene fiber of 9.7 cN / dtex or more. However, this method requires a special and expensive pressurized saturated steam drawing apparatus as compared with ordinary hot plate drawing and the like, and furthermore, the pressurized saturated steam drawing has a problem that the input amount of fibers is limited. Not suitable for mass production.

一方、紡糸条件を改良することで未延伸糸の延伸性を向上させて、ポリプロピレン繊維の高強度化を図る技術も提案されている。例えば、特開平８−９２８１３号公報（特許文献４）では紡糸工程にてメルトフローレートが１．０ｇ／１０分〜５０ｇ／１０分のポリプロピレンを溶融紡糸して得られる溶融フィラメントを冷却温度が０℃〜７０℃、風速０．１ｍ／秒〜０．５ｍ／秒の冷却ダクト内を通して体積結晶化度が２０％〜６０％、複屈折率が１．０×１０^-4〜２．０×１０^-3であるポリプロピレン未延伸糸を巻き取ったのち、延伸工程にて高延伸して、８．５ｇ／ｄ以上の高強度を有し、光沢性、透明性に優れたポリプロピレンマルチフィラメントの製造方法が開示されている。この手法によれば表面温度が−２５℃〜０℃の冷却ロールが必要であり、ロール表面での結露や生産コストの面で課題があった。 On the other hand, there has also been proposed a technique for improving the drawability of an undrawn yarn by improving the spinning conditions to increase the strength of a polypropylene fiber. For example, in Japanese Patent Application Laid-Open No. Hei 8-92213 (Patent Document 4), a molten filament obtained by melt-spinning a polypropylene having a melt flow rate of 1.0 g / 10 min to 50 g / 10 min in a spinning step has a cooling temperature of 0%. Through a cooling duct having a wind velocity of 0.1 m / sec to 0.5 m / sec and a volume crystallinity of 20% to 60% and a birefringence of 1.0 × 10 ^{-4 to} 2.0 × 10. ^-3 , a method for producing a polypropylene multifilament having high strength of 8.5 g / d or more, excellent gloss and transparency, and highly drawn in a drawing step after winding a polypropylene undrawn yarn. Is disclosed. According to this method, a cooling roll having a surface temperature of −25 ° C. to 0 ° C. is required, and there are problems in dew condensation on the roll surface and production costs.

国際公開第２０１２／１６４６５６号International Publication No. 2012/164656 特開２００３−２９３２１６号公報JP 2003-293216 A 特開２００２−１８０３４７号公報JP-A-2002-180347 特開平８−９２８１３号公報Japanese Patent Application Laid-Open No. Hei 8-92,913

本発明の目的は、特殊な冷却装置を使わずに原料・製造条件を制御して特殊な未延伸糸を得ることにより、高強度なポリプロピレン繊維の製造方法を提供することにある。 An object of the present invention is to provide a method for producing a high-strength polypropylene fiber by controlling raw materials and production conditions without using a special cooling device to obtain a special undrawn yarn.

本発明のポリプロピレン未延伸糸は、メルトフローレートが１２ｇ／分以上、２５ｇ／分以下のポリプロピレン樹脂を溶融し、該樹脂の融点から８０．６℃高い温度以上、１５０℃高い温度以下で紡糸ノズルの吐出孔から吐出して、結晶構造の割合が３０質量％以下である未延伸糸を得る、ポリプロピレン未延伸糸の製造方法である。 The unstretched polypropylene yarn of the present invention melts a polypropylene resin having a melt flow rate of 12 g / min or more and 25 g / min or less, and is spun at a temperature higher than the melting point of the resin by 80.6 ° C. or higher and 150 ° C. or lower. This is a method for producing a polypropylene undrawn yarn, which discharges from a discharge hole of a nozzle to obtain an undrawn yarn having a crystal structure ratio of 30% by mass or less.

本発明のポリプロピレン未延伸糸の製造方法は、引取り速度が２００ｍ／分以上、５００ｍ／分以下であることが好ましい。 In the method for producing an undrawn polypropylene yarn of the present invention, the take-up speed is preferably 200 m / min or more and 500 m / min or less.

本発明のポリプロピレン未延伸糸の製造方法は、前記未延伸糸の複屈折値を０．１×１０^-3以上、２．５×１０^-3以下とすることが好ましい。上記の未延伸糸を延伸することで、高強度のポリプロピレン繊維を得ることができる。 In the method for producing a polypropylene undrawn yarn of the present invention, it is preferable that the birefringence value of the undrawn yarn is 0.1 × 10 ⁻³ or more and 2.5 × 10 ⁻³ or less. By stretching the undrawn yarn, a high-strength polypropylene fiber can be obtained.

本発明のポリプロピレンの製造方法は、前記製造方法から得られる未延伸糸を１１０℃以上、１６０℃以下で延伸してポリプロピレン繊維を得る、ポリプロピレン繊維の製造方法である。 The method for producing polypropylene according to the present invention is a method for producing polypropylene fiber, wherein the unstretched yarn obtained from the production method is stretched at 110 ° C or higher and 160 ° C or lower to obtain polypropylene fiber.

本発明によれば、適切なポリプロピレン樹脂のメルトフローレート、紡糸温度、引取り速度を制御することで、結晶構造が少なく低配向な未延伸糸を得ることができる。前記未延伸糸は延伸性が高く、その結果ポリプロピレンの強度向上が可能である。 According to the present invention, by controlling the melt flow rate, spinning temperature and take-up speed of a suitable polypropylene resin, an undrawn yarn having a small crystal structure and a low orientation can be obtained. The undrawn yarn has high drawability, and as a result, the strength of polypropylene can be improved.

以下、本発明について代表的な実施の形態に基づき具体的に説明する。
●未延伸構造と延伸性について
本発明で得られる未延伸糸の結晶構造の割合は３０質量％以下である。未延伸糸の結晶構造の割合は、広角Ｘ線回折（リガク社製Ｕｌｔｒａｘ１８、波長λ＝１．５４Å）を用いて確認することができる。ポリプロピレンの構造には、結晶構造であるα晶、β晶及びγ晶と、非晶構造のほかに、結晶と非晶の中間構造であるメゾ構造があることが知られている。本発明に関わるα晶では回折角＝１４．１度、１６．９度、１８．６度、２１．６度に４本の鋭いピークが観測され、非晶構造では回折角＝１６度にブロードなアモルファスピークが、メゾ構造では回折角＝１５度と２１度にややブロードなピークが観測され（非特許文献Ｍａｃｒｏｍｏｌｅｃｕｌｅｓ２００５、３８、８７４９−８７５４）、波形分離することでそれぞれの構造の割合を算出することができる。具体的には未延伸糸の広角Ｘ線回折パターンについて、回折角＝１４．１度、１６．９度、１８．６度、２１．６度（結晶構造）、１６度（非晶構造）、１５度、２１度（メゾ構造）にそれぞれピークを設置して波形分離を行い、結晶構造のピーク積分強度の和をすべてのピーク積分強度で除すことで、結晶構造の割合を算出することができる。 Hereinafter, the present invention will be specifically described based on typical embodiments.
● About undrawn structure and drawability The ratio of the crystal structure of the undrawn yarn obtained in the present invention is 30% by mass or less. The ratio of the crystal structure of the undrawn yarn can be confirmed using wide-angle X-ray diffraction (Ultrax 18, manufactured by Rigaku Corporation, wavelength λ = 1.54 °). It is known that the structure of polypropylene includes a crystal structure, α-crystal, β-crystal, and γ-crystal, and an amorphous structure, as well as a meso-structure, which is an intermediate structure between the crystal and the amorphous. In the α-crystal according to the present invention, four sharp peaks were observed at diffraction angles of 14.1 °, 16.9 °, 18.6 °, and 21.6 °, and in the amorphous structure, the diffraction angle was broad at 16 °. In the mesostructure, a non-patent document Macromolecules 2005, 38, 8749-8754, a slightly amorphous peak is observed at a diffraction angle of 15 degrees and 21 degrees in the meso structure, and the ratio of each structure is calculated by waveform separation. can do. Specifically, regarding the wide-angle X-ray diffraction pattern of the undrawn yarn, the diffraction angles are 14.1 degrees, 16.9 degrees, 18.6 degrees, 21.6 degrees (crystal structure), 16 degrees (amorphous structure), Waveform separation is performed by setting peaks at 15 degrees and 21 degrees (meso structure), respectively, and the ratio of the crystal structure can be calculated by dividing the sum of the peak integrated intensities of the crystal structure by all the peak integrated intensities. it can.

未延伸糸の結晶構造の割合は延伸性の観点から、３０質量％以下である。
未延伸糸の結晶構造の割合が３０質量％以下であれば、延伸性が高くなり、延伸糸の強度を高くできる。前記観点から、未延伸糸の結晶構造の割合は２０質量％以下がより好ましく、１０質量％以下がさらに好ましい。一般的に結晶構造であるα晶は折り畳み構造を取る。後の延伸工程でこの折り畳み構造は伸び切り鎖へと変換されるが、メゾ構造や非晶構造に比べて、一度形成された折り畳み構造を伸び切り鎖へと変換するのはエネルギー的に不利である。結果として、メゾ構造や非晶構造に比べて、α晶の場合は延伸性が低下する。 The ratio of the crystal structure of the undrawn yarn is 30% by mass or less from the viewpoint of drawability.
When the proportion of the crystal structure of the undrawn yarn is 30% by mass or less, the drawability is increased, and the strength of the drawn yarn can be increased. In this respect, the proportion of the crystal structure of the undrawn yarn is more preferably equal to or less than 20% by mass, and still more preferably equal to or less than 10% by mass. In general, an α-crystal having a crystal structure has a folded structure. In the subsequent stretching step, this folded structure is converted into an extended chain.However, it is energetically disadvantageous to convert the once formed folded structure into an extended chain as compared with a mesostructure or an amorphous structure. is there. As a result, the drawability of α-crystals is lower than that of mesostructures or amorphous structures.

複屈折値はポリプロピレン分子の配向状態を定量化したものであり、複屈折値が小さいほど分子配向が低いことを示している。未延伸糸の分子配向が小さければ、後の延伸工程で高倍率に延伸することが可能であり、高強度なポリプロピレン繊維を得ることができる。得られる未延伸糸の複屈折値は、０．１×１０^-3以上、２．５×１０^-3以下が好ましい。複屈折値が０．１×１０^-3以上の未延伸糸は、工業的に製造可能である。一方、複屈折値が２．５×１０^-3以下の未延伸糸は、延伸工程で高倍率に延伸することができ、得られるポリプロピレン繊維の強度は向上する。未延伸糸の複屈折値は０．６×１０^-3以上、２．０×１０^-3以下であることがより好ましく、０．９×１０^-3以上、１．５×１０^-3以下がさらに好ましい。 The birefringence value is a quantification of the orientation state of the polypropylene molecule, and a smaller birefringence value indicates a lower molecular orientation. If the molecular orientation of the undrawn yarn is small, it is possible to draw at a high magnification in a subsequent drawing step, and a high-strength polypropylene fiber can be obtained. The birefringence value of the obtained undrawn yarn is preferably 0.1 × 10 ⁻³ or more and 2.5 × 10 ⁻³ or less. An undrawn yarn having a birefringence value of 0.1 × 10 ⁻³ or more can be industrially produced. On the other hand, an undrawn yarn having a birefringence of 2.5 × 10 ⁻³ or less can be drawn at a high magnification in the drawing step, and the strength of the obtained polypropylene fiber is improved. The birefringence value of the undrawn yarn is preferably 0.6 × 10 ⁻³ or more and 2.0 × 10 ⁻³ or less, more preferably 0.9 × 10 ⁻³ or more and 1.5 × 10 ⁻³ or less. More preferred.

●原料について
本発明のポリプロピレン繊維の原料であるポリプロピレン樹脂のメルトフローレート（以下、ＭＦＲという。）〔ＪＩＳＫ７２０１に従って温度２３０℃、荷重２．１６ｋｇ、時間１０分間の条件で測定〕は、１２ｇ／分以上、２８ｇ／分以下である。ＭＦＲが１２ｇ／分以上であれば溶融粘度が高くなり過ぎず紡糸線上での張力が高くならないため、配向結晶化を抑制できる。そのため得られる未延伸糸は結晶構造の割合が高くならず、複屈折値も低くできる。 ● Raw Material The melt flow rate (hereinafter referred to as MFR) of the polypropylene resin, which is the raw material of the polypropylene fiber of the present invention, is 12 g according to JIS K 7201 at a temperature of 230 ° C., a load of 2.16 kg and a time of 10 minutes. / Min or more and 28 g / min or less. If the MFR is 12 g / min or more, the melt viscosity does not become too high and the tension on the spinning line does not increase, so that the orientation crystallization can be suppressed. Therefore, the resulting undrawn yarn does not have a high crystal structure ratio and can have a low birefringence value.

一方、ＭＦＲが２８ｇ／分以下であれば、溶融粘度が低下し過ぎず、必要な紡糸線張力を得ることができる。しかし、一般的にＭＦＲが高いポリプロピレン樹脂は分子量が低いため、ポリプロピレン樹脂の結晶化速度が速くなり、得られる未延伸糸は結晶構造の割合が高くなる。ポリプロピレン樹脂のＭＦＲは１４ｇ／分以上、２５ｇ／分以下であることが好ましく、１６ｇ／分以上、２２ｇ／分以下がさらに好ましい。 On the other hand, when the MFR is 28 g / min or less, the melt viscosity does not excessively decrease, and a necessary spinning wire tension can be obtained. However, since the polypropylene resin having a high MFR generally has a low molecular weight, the crystallization speed of the polypropylene resin is increased, and the resulting undrawn yarn has a high crystal structure ratio. The MFR of the polypropylene resin is preferably from 14 g / min to 25 g / min, and more preferably from 16 g / min to 22 g / min.

本発明に用いるポリプロピレン樹脂のアイソタクチックペンタッド率は９４質量％以上９９質量％以下であることが好ましい。９４質量％以上であればポリプロピレン繊維は均一な結晶構造を形成することが容易となり、一方で９９質量％以下であればポリプロピレン繊維を工業的に得ることは可能である。 The isotactic pentad ratio of the polypropylene resin used in the present invention is preferably from 94% by mass to 99% by mass. When the content is 94% by mass or more, the polypropylene fiber can easily form a uniform crystal structure. On the other hand, when the content is 99% by mass or less, the polypropylene fiber can be obtained industrially.

ポリプロピレン樹脂の分子量分布は５以下であることが好ましい。分子量分布が５以下であればポリプロピレン繊維は均一な結晶構造を取ることができ、繊維強度が向上する。分子量分布は４以下がより好ましい。 The molecular weight distribution of the polypropylene resin is preferably 5 or less. When the molecular weight distribution is 5 or less, the polypropylene fiber can have a uniform crystal structure, and the fiber strength is improved. The molecular weight distribution is more preferably 4 or less.

本発明に用いるポリプロピレン樹脂には、本発明の効果を妨げない範囲内で、更に酸化防止剤、光安定剤、紫外線吸収剤、中和剤、造核剤、エポキシ安定剤、滑剤、抗菌剤、難燃剤、帯電防止剤、顔料、可塑剤などの添加剤を適宜必要に応じて添加してもよい。 In the polypropylene resin used in the present invention, as long as the effects of the present invention are not impaired, an antioxidant, a light stabilizer, an ultraviolet absorber, a neutralizing agent, a nucleating agent, an epoxy stabilizer, a lubricant, an antibacterial agent, Additives such as a flame retardant, an antistatic agent, a pigment, and a plasticizer may be appropriately added as necessary.

●紡糸・延伸
上述のようなポリプロピレン原料を押出機に投入して混練した後、ギアポンプにて定量的に紡糸ノズルの吐出孔から吐出させる。紡糸温度はポリプロピレン原料の融点から６０℃高い温度以上、１５０℃高い温度以下で、紡糸ノズルの吐出孔から吐出させることが好ましい。紡糸温度が融点より６０℃高い温度以上であれば、紡糸線上の溶融粘度が高くなり過ぎず配向結晶化が抑制されるため、得られる未延伸糸の結晶構造の割合が低減でき、複屈折値も低くできる。そのため延伸性が良好となり、繊維強度を高くすることができる。一方、ポリプロピレン原料の融点よりも１５０℃高い温度以下であれば、原料自体の分解が進行し難くなるため強度が低下しない。融点から８０℃高い温度以上、１２０℃高い温度以下で紡糸するのがより好ましい。 ● Spinning / Drawing After the above-mentioned polypropylene raw material is put into an extruder and kneaded, the mixture is quantitatively discharged from a discharge hole of a spinning nozzle by a gear pump. The spinning temperature is preferably higher than the melting point of the polypropylene raw material by 60 ° C. or higher and lower by 150 ° C. or lower, and is preferably discharged from the discharge hole of the spinning nozzle. If the spinning temperature is at least 60 ° C. higher than the melting point, the melt viscosity on the spinning line will not be too high and orientation crystallization will be suppressed, so that the ratio of the crystal structure of the obtained undrawn yarn can be reduced, and the birefringence value can be reduced. Can also be lowered. Therefore, the stretchability becomes good and the fiber strength can be increased. On the other hand, if the temperature is 150 ° C. or lower than the melting point of the polypropylene raw material, the raw material itself does not easily decompose, so that the strength does not decrease. It is more preferable to spin at a temperature higher than the melting point by 80 ° C. or higher and 120 ° C. or lower.

紡糸ノズルの吐出孔（以下、「ホール」という場合がある。）から吐出するポリマーの吐出量は１ホールあたり、０．１ｇ／分以上、３ｇ／分以下が好ましい。前記吐出量が０．１ｇ／分以上であれば、クエンチ筒での冷風により糸揺れが大きくならず、フィラメント間での融着やガイドへの接触が起こり難く、安定的に未延伸糸を得ることができる。一方、前記吐出量が３ｇ／分以下であれば、クエンチ筒での繊維の冷却が十分でき、引取りの際にフィラメント間での融着が起こり難く、安定的に未延伸糸が得られる。前記吐出量は前記観点から１．０ｇ／分以上、２．５ｇ／分以下が好ましく、１．２ｇ／分以上、２．０ｇ／分以下がさらに好ましい。 The discharge amount of the polymer discharged from the discharge hole of the spinning nozzle (hereinafter sometimes referred to as “hole”) is preferably 0.1 g / min or more and 3 g / min or less per hole. When the discharge rate is 0.1 g / min or more, the yarn sway does not increase due to the cold air in the quench tube, the fusion between the filaments and the contact with the guide hardly occur, and the undrawn yarn is stably obtained. be able to. On the other hand, if the discharge rate is 3 g / min or less, the fibers can be sufficiently cooled in the quench tube, and fusion between the filaments does not easily occur during take-off, and an undrawn yarn can be stably obtained. The discharge rate is preferably 1.0 g / min or more and 2.5 g / min or less, more preferably 1.2 g / min or more and 2.0 g / min or less from the above viewpoint.

ノズルから押し出された繊維は、クエンチ筒で１０℃以上、４０℃以下の冷風を当てて急冷される。冷風は繊維の冷却を進行させ、糸揺れによる繊維の融着が起きないという観点から、その風速は０．５ｍ／秒以上、５ｍ／秒以下の範囲が好ましい。その後冷却固化した繊維に、適宜オイリング装置で油剤を付与する。 The fiber extruded from the nozzle is quenched in a quench tube by applying cold air of 10 ° C or more and 40 ° C or less. From the viewpoint that the cold wind advances the cooling of the fiber and does not cause fusion of the fiber due to yarn sway, the wind speed is preferably in a range of 0.5 m / sec or more and 5 m / sec or less. Thereafter, an oil agent is appropriately applied to the cooled and solidified fiber by an oiling device.

紡糸ドラフトは５以上、１５０以下であることが好ましい。ここで紡糸ドラフトは吐出線速度（ｍ／分）と引取り速度（ｍ／分）で求めることができる。紡糸ドラフトが５以上であれば、紡糸線上で張力が付与されるため、安定的に未延伸糸を得ることができる。一方、紡糸ドラフトが１５０以下であれば、紡糸線上で張力が高くなりすぎず配向結晶化が抑制され、得られる未延伸糸は低結晶化度、低配向になるため、延伸性が向上する。 The spinning draft is preferably 5 or more and 150 or less. Here, the spinning draft can be determined from the discharge linear speed (m / min) and the take-up speed (m / min). If the spinning draft is 5 or more, a tension is applied on the spinning wire, so that an undrawn yarn can be stably obtained. On the other hand, if the spinning draft is at most 150, the tension on the spinning line will not be too high, and the orientation and crystallization will be suppressed.

未延伸糸の引取り速度は２００ｍ／分以上、５００ｍ／分以下が好ましい。前記引取り速度が２００ｍ／分以上であれば十分な生産性が得られる。一方、前記引取り速度が５００ｍ／分以下であれば、紡糸線上の張力が高くなり過ぎず、目的の未延伸構造を得易くなる。未延伸糸の引取り速度は２５０ｍ／分以上、４５０ｍ／分以下であることがより好ましく、２８０ｍ／分以上、３５０ｍ／分以下がさらに好ましい。 The take-up speed of the undrawn yarn is preferably 200 m / min or more and 500 m / min or less. If the take-off speed is 200 m / min or more, sufficient productivity can be obtained. On the other hand, if the take-up speed is 500 m / min or less, the tension on the spinning line does not become too high, and it becomes easy to obtain a desired undrawn structure. The take-up speed of the undrawn yarn is preferably from 250 m / min to 450 m / min, more preferably from 280 m / min to 350 m / min.

未延伸糸の延伸は、一度巻き取った未延伸糸をオフラインで行っても良いし、紡糸工程から一旦巻き取ることなしにそのまま引き続いて行っても良い。また延伸には熱板延伸、熱ロール延伸、熱風炉延伸など公知の方法で延伸することができる。 The stretching of the undrawn yarn may be performed off-line with the undrawn yarn once wound up, or may be continuously performed without being wound up once from the spinning step. The stretching can be performed by a known method such as hot plate stretching, hot roll stretching, and hot air oven stretching.

延伸温度は１１０℃以上、１６０℃以下の範囲で行うのが好ましい。ここで延伸温度とは糸の実際の温度である。延伸温度が１１０℃以上であれば、ポリプロピレン未延伸糸の結晶分散温度よりも高くなるため分子運動が活発化し、高倍率で延伸することが可能である。一方、延伸温度が１６０℃以下であれば、繊維が融着せず、延伸自体が容易にできる。前記延伸温度は１２０℃以上、１５５℃以下がより好ましく、１４０℃以上１５５℃以下がさらに好ましい。 The stretching temperature is preferably from 110 ° C. to 160 ° C. Here, the drawing temperature is the actual temperature of the yarn. When the stretching temperature is 110 ° C. or higher, the molecular motion is activated because the temperature is higher than the crystal dispersion temperature of the polypropylene undrawn yarn, and it is possible to draw at a high magnification. On the other hand, when the stretching temperature is 160 ° C. or lower, the fibers are not fused, and the stretching itself can be easily performed. The stretching temperature is more preferably from 120 ° C to 155 ° C, and still more preferably from 140 ° C to 155 ° C.

延伸の前に繊維を予備加熱してもよい。延伸前の予備加熱は加熱ロールや、熱板、熱風炉などを使用することができる。予備加熱の温度は５０℃以上、１２０℃以下、より好ましくは６０℃以上、１１０℃以下である。 The fiber may be preheated before drawing. For preheating before stretching, a heating roll, a hot plate, a hot air oven, or the like can be used. The preheating temperature is 50 ° C or higher and 120 ° C or lower, more preferably 60 ° C or higher and 110 ° C or lower.

本発明で得られる未延伸糸は高倍率で延伸が可能であり、高強度化の繊維を得ることができる。延伸倍率は、実際に延伸を行う温度での最大破断延伸倍率の０．５倍以上、０．９倍以下で行うことが好ましい。延伸倍率が最大破断延伸倍率の０．５倍以上であれば強度が高くでき、一方で最大破断延伸倍率の０．９倍以下であれば毛羽や糸切れが起こり難く安定的に延伸できる。前記延伸倍率は延伸温度での最大破断延伸倍率の０．５５倍以上、０．８５倍以下がより好ましく、０．６倍以上、０．８倍以下がさらに好ましい。 The undrawn yarn obtained in the present invention can be drawn at a high magnification, and a fiber with high strength can be obtained. The stretching ratio is preferably 0.5 to 0.9 times the maximum breaking stretching ratio at the temperature at which the stretching is actually performed. If the stretching ratio is 0.5 times or more of the maximum breaking stretching ratio, the strength can be increased, while if it is 0.9 times or less of the maximum breaking stretching ratio, fluff and yarn breakage are less likely to occur and stable stretching can be performed. The stretch ratio is more preferably 0.55 times or more and 0.85 times or less, more preferably 0.6 times or more and 0.8 times or less of the maximum breaking stretch ratio at the stretching temperature.

延伸速度は１００ｍ／分以上、１０００ｍ／分以下であることが好ましい。ここで延伸速度とは、延伸する際の引取り速度のことである。延伸速度が１００ｍ／分以上であれば十分な生産性が得られる。一方、延伸速度が１０００ｍ／分以下であれば変形速度が速くなり過ぎないため、安定した延伸が可能となる。前記延伸速度は１５０ｍ／分以上、８００ｍ／分以下が好ましく、２００ｍ／分以上、６００ｍ／分以下がさらに好ましい。 The stretching speed is preferably 100 m / min or more and 1000 m / min or less. Here, the stretching speed is a take-up speed at the time of stretching. If the stretching speed is 100 m / min or more, sufficient productivity can be obtained. On the other hand, if the stretching speed is 1000 m / min or less, the deformation speed does not become too high, so that stable stretching is possible. The stretching speed is preferably from 150 m / min to 800 m / min, more preferably from 200 m / min to 600 m / min.

上述したように、適切なメルトフローレートのポリプロピレン樹脂を、融点から８０．６℃高い温度以上、１５０℃高い温度以下の温度で溶融し、紡糸して、２００ｍ／分以上、５００ｍ／分以下で引取ることで、結晶構造の割合が低く、低配向な未延伸糸を得ることができる。このようにして得られた未延伸糸は高倍率で延伸することができる。得られるポリプロピレン繊維の強度は６．８ｃＮ／ｄｔｅｘを超える強度を得ることができる。 As described above, a polypropylene resin having an appropriate melt flow rate is melted at a temperature higher than the melting point by 80.6 ° C. or higher and 150 ° C. or lower, spun, and spun at a temperature of 200 m / min or more and 500 m / min or less. By taking off, an undrawn yarn having a low crystal structure and a low orientation can be obtained. The undrawn yarn thus obtained can be drawn at a high magnification. The strength of the obtained polypropylene fiber can be higher than 6.8 cN / dtex.

以下、実施例及び比較例により本発明をより具体的に説明するが、本発明は以下の実施例に何ら限定されるものではない。
実施例においてポリプロピレン樹脂の融点、広角Ｘ線回折、複屈折値、繊維強度は、以下の方法で測定した。
ポリプロピレン樹脂の融点はＤＳＣ装置（エスアイアイ・ナノテクノロジー社製ＤＳＣ２２０）を用いて算出した。ポリプロピレン樹脂ペレットを細かく切断してサンプルパンに１０ｍｇ投入した。窒素雰囲気下で昇温速度１０℃／分で室温から２４０℃で測定を行った。得られたＤＳＣカーブのピークトップの温度を融点とした。 Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
In Examples, the melting point, wide-angle X-ray diffraction, birefringence, and fiber strength of the polypropylene resin were measured by the following methods.
The melting point of the polypropylene resin was calculated using a DSC device (DSI Nanotechnology, Inc., DSC220). The polypropylene resin pellet was cut into small pieces and 10 mg was put into a sample pan. The measurement was performed from room temperature to 240 ° C. at a rate of 10 ° C./min in a nitrogen atmosphere. The temperature at the peak top of the obtained DSC curve was defined as the melting point.

未延伸糸の構造解析は広角Ｘ線回折測定装置（リガク社製Ｕｌｔｒａｘ１８、波長λ＝１．５４Å）を用いて行った。未延伸糸を約５ｃｍになるように切断して、３０ｍｇになるように調製した。繊維を１軸方向に引き揃えて、サンプルホルダーに取り付けた。管電圧は４０ｋＶ、管電流は２００ｍＡ、照射時間は３０分で測定した。
得られた２次元回折像を、全方位について１次元プロファイルを切り出した後、バックグランドを差し引いて、最終的な１次元プロファイルとした。結晶構造の割合については、上述した方法で実施した。なお、フィッティングしたピーク関数は、ガウス関数とローレンツ関数の重ね合わせである疑似フォークト関数を用い、ガウス関数とローレンツ関数の比を１：１に固定した。 The structural analysis of the undrawn yarn was performed using a wide-angle X-ray diffractometer (Ultrax 18, manufactured by Rigaku Corporation, wavelength λ = 1.54 °). The undrawn yarn was cut so as to be about 5 cm, and was prepared so as to be 30 mg. The fibers were uniaxially aligned and attached to a sample holder. The tube voltage was 40 kV, the tube current was 200 mA, and the irradiation time was 30 minutes.
From the obtained two-dimensional diffraction image, a one-dimensional profile was cut out in all directions, and the background was subtracted to obtain a final one-dimensional profile. About the ratio of a crystal structure, it implemented by the method mentioned above. The fitted peak function used a pseudo Voigt function, which is a superposition of a Gaussian function and a Lorentz function, and the ratio of the Gaussian function to the Lorentz function was fixed at 1: 1.

未延伸糸の複屈折値は偏光顕微鏡（ニコン社製ＥＣＬＩＰＳＥＥ６００）を用いて算出した。波長が５４６ｎｍになるように干渉フィルターを入れて、レタデーション測定を行った。得られたレタデーションを繊維直径で除することで、複屈折値を算出した。繊維直径は未延伸糸の繊度と密度（０．９１ｇ／ｃｍ³）から算出した。５回測定を行い、平均値を使用した。 The birefringence value of the undrawn yarn was calculated using a polarizing microscope (Nikon ECLIPSE E600). An interference filter was inserted so that the wavelength became 546 nm, and retardation measurement was performed. Birefringence value was calculated by dividing the obtained retardation by the fiber diameter. The fiber diameter was calculated from the fineness and density (0.91 g / cm ³ ) of the undrawn yarn. Five measurements were made and the average was used.

繊維強度はＪＩＳＬ１０１３に準じて行った。引張試験機（島津社製ＡＧ−ＩＳ）を用い、試料長２００ｍｍ、引張速度１００％／分の条件で歪−応力曲線を雰囲気温度２０℃、相対湿度６５％条件下で測定し、破断点での応力から強度を求めた。５回測定を行い、平均値を使用した。 Fiber strength was measured according to JIS L 1013. Using a tensile tester (AG-IS manufactured by Shimadzu Corporation), a strain-stress curve was measured under the conditions of a sample length of 200 mm and a tensile speed of 100% / min under an atmosphere temperature of 20 ° C. and a relative humidity of 65%. The strength was determined from the stress of. Five measurements were made and the average was used.

以下、実施例１〜１０及び比較例１〜３に基づいて本発明を更に具体的に説明する。表１は、各実施例１〜１０及び各比較例１〜３におけるポリプロピレン未延伸糸の各製造条件及びその製造方法により得られた未延伸糸の物性を表１に示す。 Hereinafter, the present invention will be described more specifically based on Examples 1 to 10 and Comparative Examples 1 to 3. Table 1 shows the production conditions of the polypropylene undrawn yarns in Examples 1 to 10 and Comparative Examples 1 to 3 and the physical properties of the undrawn yarns obtained by the production method.

（実施例１）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．４ｍｍφ、２４ホール）から３４ｇ／分の吐出量（１ホールあたり１．４ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。未延伸糸の複屈折値は１．３０×１０^-3、結晶構造の割合は０質量％だった。この未延伸糸の１５５℃での最大破断延伸倍率は１１．６倍だった。予備加熱温度８５℃、熱板温度１５５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、得られたポリプロピレン繊維の強度は表１に示すとおり７．９ｃＮ／ｄｔｅｘだった。 (Example 1)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melt-kneaded and discharged from a 280 ° C. nozzle (0.4 mmφ, 24 holes) at a discharge rate of 34 g / min (1.4 g / min per hole). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 1.30 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum breaking draw ratio at 155 ° C. of this undrawn yarn was 11.6 times. When stretched at a preheating temperature of 85 ° C. and a hot plate temperature of 155 ° C. at a rate of 300 m / min at 0.7 times the maximum breaking stretch ratio, the strength of the obtained polypropylene fiber was 7.9 cN / dtex as shown in Table 1. was.

（実施例２）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．８ｍｍφ、２０ホール）から３０ｇ／分の吐出量（１ホールあたり１．５ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。未延伸糸の複屈折値は０．９２×１０^-3、結晶構造の割合は０質量％だった。この未延伸糸の１５５℃での最大破断延伸倍率は１１．４倍だった。予備加熱温度８５℃、熱板温度１５５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は７．７ｃＮ／ｄｔｅｘだった。 (Example 2)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melt-kneaded and discharged at a discharge rate of 30 g / min (1.5 g / min per hole) from a 280 ° C. nozzle (0.8 mmφ, 20 holes). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.92 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum breaking draw ratio at 155 ° C. of this undrawn yarn was 11.4 times. When stretched at a preheating temperature of 85 ° C. and a hot plate temperature of 155 ° C. at a speed of 300 m / min at 0.7 times the maximum breaking stretch ratio, the strength of the polypropylene fiber obtained as shown in Table 1 was 7.7 cN / dtex. was.

（実施例３）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．５ｍｍφ、２０ホール）から４６ｇ／分の吐出量（１ホールあたり２．３ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。未延伸糸の複屈折値は０．８８×１０^-3、結晶構造の割合は０質量％だった。この未延伸糸の１５５℃での最大破断延伸倍率は１１．９倍だった。予備加熱温度８５℃、熱板温度１５５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は７．４ｃＮ／ｄｔｅｘだった。 (Example 3)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melted and kneaded, and discharged from a 280 ° C. nozzle (0.5 mmφ, 20 holes) at a discharge rate of 46 g / min (2.3 g / min per hole). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.88 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum breaking draw ratio at 155 ° C. of this undrawn yarn was 11.9 times. When the film was drawn at a preheating temperature of 85 ° C. and a hot plate temperature of 155 ° C. at a speed of 300 m / min at 0.7 times the maximum breaking draw ratio, the strength of the polypropylene fiber obtained as shown in Table 1 was 7.4 cN / dtex. was.

（実施例４）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．５ｍｍφ、２０ホール）から３０ｇ／分の吐出量（１ホールあたり１．５ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。未延伸糸の複屈折値は０．８８×１０^-3、結晶構造の割合は０質量％だった。この未延伸糸の１３５℃での最大破断延伸倍率は１０．３倍だった。予備加熱温度８５℃、熱板温度１３５℃、最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は７．３ｃＮ／ｄｔｅｘだった。 (Example 4)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melt-kneaded and discharged from a 280 ° C. nozzle (0.5 mmφ, 20 holes) at a discharge rate of 30 g / min (1.5 g / min per hole). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.88 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum breaking draw ratio at 135 ° C. of this undrawn yarn was 10.3 times. When the film was drawn at a preheating temperature of 85 ° C, a hot plate temperature of 135 ° C, and 0.7 times the maximum breaking draw ratio at a speed of 300 m / min, the strength of the polypropylene fiber obtained as shown in Table 1 was 7.3 cN / dtex. was.

（実施例５）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．５ｍｍφ、２０ホール）から３０ｇ／分の吐出量（１ホールあたり１．５ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。未延伸糸の複屈折値は０．８８×１０^-3、結晶構造の割合は０質量％だった。この未延伸糸の１５５℃での最大破断延伸倍率は１０．９倍だった。予備加熱温度８５℃、熱板温度１５５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は７．１ｃＮ／ｄｔｅｘだった。 (Example 5)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melt-kneaded and discharged from a 280 ° C. nozzle (0.5 mmφ, 20 holes) at a discharge rate of 30 g / min (1.5 g / min per hole). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.88 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum breaking draw ratio at 155 ° C. of this undrawn yarn was 10.9 times. When stretched at a preheating temperature of 85 ° C. and a hot plate temperature of 155 ° C. at a speed of 300 m / min at 0.7 times the maximum breaking stretch ratio, the strength of the polypropylene fiber obtained as shown in Table 1 was 7.1 cN / dtex. was.

（実施例６）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．３ｍｍφ、２０ホール）から４６ｇ／分の吐出量（１ホールあたり２．３ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。未延伸糸の複屈折値は０．７６×１０^-3、結晶構造の割合は０質量％だった。この未延伸糸の１５５℃での最大破断延伸倍率は１１．６倍だった。予備加熱温度８５℃、熱板温度１５５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は７．１ｃＮ／ｄｔｅｘだった。 (Example 6)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melt-kneaded and discharged at a discharge rate of 46 g / min (2.3 g / min per hole) from a 280 ° C. nozzle (0.3 mmφ, 20 holes). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.76 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum breaking draw ratio at 155 ° C. of this undrawn yarn was 11.6 times. When stretched at a preheating temperature of 85 ° C. and a hot plate temperature of 155 ° C. at a speed of 300 m / min at 0.7 times the maximum breaking stretch ratio, the strength of the polypropylene fiber obtained as shown in Table 1 was 7.1 cN / dtex. was.

（実施例７）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．４ｍｍφ、２４ホール）から３４ｇ／分の吐出量（１ホールあたり１．４ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。この未延伸糸の複屈折値は１．３０×１０^-3、結晶構造の割合は０質量％だった。この未延伸糸の１３５℃での最大破断延伸倍率は１０．４倍だった。未延伸糸を予備加熱温度８５℃、熱板温度１３５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は７．１ｃＮ／ｄｔｅｘだった。 (Example 7)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melt-kneaded and discharged from a 280 ° C. nozzle (0.4 mmφ, 24 holes) at a discharge rate of 34 g / min (1.4 g / min per hole). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of this undrawn yarn was 1.30 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum breaking draw ratio at 135 ° C. of this undrawn yarn was 10.4 times. When the undrawn yarn was drawn at a preheating temperature of 85 ° C and a hot plate temperature of 135 ° C at a rate of 0.7 times the maximum breaking draw ratio at a speed of 300 m / min, the strength of the polypropylene fiber obtained as shown in Table 1 was 7 It was .1 cN / dtex.

（実施例８）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．５ｍｍφ、２０ホール）から４６ｇ／分の吐出量（１ホールあたり２．３ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。未延伸糸の複屈折値は０．８８×１０^-3、結晶構造の割合は０質量％だった。この未延伸糸の１３５℃での最大破断延伸倍率は１０．９倍だった。予備加熱温度８５℃、熱板温度１３５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は６．９ｃＮ／ｄｔｅｘだった。 (Example 8)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melted and kneaded, and discharged from a 280 ° C. nozzle (0.5 mmφ, 20 holes) at a discharge rate of 46 g / min (2.3 g / min per hole). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.88 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum draw ratio at 135 ° C. of the undrawn yarn was 10.9 times. When stretched at a preheating temperature of 85 ° C. and a hot plate temperature of 135 ° C. at a rate of 300 m / min at 0.7 times the maximum breaking stretch ratio, the strength of the polypropylene fiber obtained as shown in Table 1 was 6.9 cN / dtex. was.

（実施例９）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２５０℃で溶融混練し、２５０℃のノズル（０．３ｍｍφ、２０ホール）から３０ｇ／分の吐出量（１ホールあたり１．５ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。この未延伸糸の複屈折値は２．０２×１０^-3、結晶構造の割合は１６．０質量％だった。未延伸糸の１５５℃での最大破断延伸倍率は１０．１倍だった。予備加熱温度８５℃、熱板温度１５５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は７．３ｃＮ／ｄｔｅｘだった。 (Example 9)
A polypropylene resin (Y2000GV, manufactured by Prime Polymer Co., Ltd., melting point of 169.4 ° C., MFR = 18 g / min [230 ° C., load 2.16 kg, 10 minutes]) is charged into an extruder of a melt spinning device, and is heated at 250 ° C. The mixture was melted and kneaded, and discharged at a discharge rate of 30 g / min (1.5 g / min per hole) from a 250 ° C. nozzle (0.3 mmφ, 20 holes). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of this undrawn yarn was 2.02 × 10 ⁻³ , and the ratio of the crystal structure was 16.0% by mass. The maximum breaking draw ratio at 155 ° C. of the undrawn yarn was 10.1 times. When stretched at a preheating temperature of 85 ° C. and a hot plate temperature of 155 ° C. at a speed of 300 m / min at 0.7 times the maximum breaking stretch ratio, the strength of the polypropylene fiber obtained as shown in Table 1 was 7.3 cN / dtex. was.

（実施例１０）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．３ｍｍφ、２０ホール）から３０ｇ／分の吐出量（１ホールあたり１．５ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で６００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。この未延伸糸の複屈折値は３．１５×１０^-3、結晶構造の割合は０質量％だった。未延伸糸の１３５℃での最大破断延伸倍率は９．３倍だった。予備加熱温度８５℃、熱板温度１３５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、表１に示すとおり得られたポリプロピレン繊維の強度は６．７ｃＮ／ｄｔｅｘだった。 (Example 10)
A polypropylene resin (Y2000GV manufactured by Prime Polymer Co., Ltd., melting point of the resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and then heated at 280 ° C. The mixture was melt-kneaded and discharged at a discharge rate of 30 g / min (1.5 g / min per hole) from a 280 ° C. nozzle (0.3 mmφ, 20 holes). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered and wound on a bobbin at room temperature at a take-up speed of 600 m / min to obtain an undrawn yarn. The birefringence value of this undrawn yarn was 3.15 × 10 ⁻³ , and the ratio of the crystal structure was 0% by mass. The maximum breaking draw ratio at 135 ° C. of the undrawn yarn was 9.3 times. When stretched at a preheating temperature of 85 ° C. and a hot plate temperature of 135 ° C. at a rate of 300 m / min at 0.7 times the maximum breaking stretch ratio, the strength of the polypropylene fiber obtained as shown in Table 1 was 6.7 cN / dtex. was.

（比較例１）
ポリプロピレン樹脂（日本ポリプロ社製ＳＡ０１Ａ、樹脂の融点１６８．３℃、ＭＦＲ＝１０ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．４ｍｍφ、２４ホール）から３４ｇ／分の吐出量（１ホールあたり１．４ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。この未延伸糸の複屈折値は２．３６×１０^-3、結晶構造の割合は４６．０質量％だった。この未延伸糸の１３５℃での最大破断延伸倍率は９．３倍だった。予備加熱温度８５℃、熱板温度１３５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、得られたポリプロピレン繊維の強度は表１に示すとおり６．７ｃＮ／ｄｔｅｘと低かった。これはＭＦＲが１０ｇ／分と低いため溶融粘度が高く、紡糸線上での張力が高くなり、得られる未延伸糸の結晶構造の割合が増加し、α晶の配向結晶化が促進されたがためであると考えられる。 (Comparative Example 1)
A polypropylene resin (SA01A, manufactured by Nippon Polypropylene Co., Ltd., melting point of 168.3 ° C., MFR = 10 g / min [230 ° C., load 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and heated at 280 ° C. The mixture was melt-kneaded and discharged from a 280 ° C. nozzle (0.4 mmφ, 24 holes) at a discharge rate of 34 g / min (1.4 g / min per hole). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of this undrawn yarn was 2.36 × 10 ⁻³ , and the ratio of the crystal structure was 46.0% by mass. The maximum breaking draw ratio at 135 ° C. of this undrawn yarn was 9.3 times. When stretched at a preheating temperature of 85 ° C and a hot plate temperature of 135 ° C at a rate of 0.7 times the maximum breaking stretch ratio at a speed of 300 m / min, the strength of the obtained polypropylene fiber was 6.7 cN / dtex as shown in Table 1. Was low. This is because the melt viscosity is high because the MFR is as low as 10 g / min, the tension on the spinning wire is high, the ratio of the crystal structure of the obtained undrawn yarn is increased, and the oriented crystallization of α crystals is promoted. It is considered to be.

（比較例２）
ポリプロピレン樹脂（日本ポリプロ社製ＳＡ０３Ａ、樹脂の融点１６８．７℃、ＭＦＲ＝３０ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２８０℃で溶融混練し、２８０℃のノズル（０．４ｍｍφ、２４ホール）から３４ｇ／分の吐出量（１ホールあたり１．４ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。この未延伸糸の複屈折値は１．０６×１０^-3、結晶構造の割合は４０．１質量％だった。未延伸糸の１３５℃での最大破断延伸倍率は１１．２倍だった。予備加熱温度８５℃、熱板温度１３５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、得られたポリプロピレン繊維の強度は、表１に示すとおり６．５ｃＮ／ｄｔｅｘであって、上述の実施例１〜１０のいずれよりも低かった。これは複屈折値は低いものの、結晶構造がα晶である上に、ＭＦＲが極めて高いため、所要の強度が得られなかったと考えられる。 (Comparative Example 2)
A polypropylene resin (SA03A, manufactured by Nippon Polypropylene Co., Ltd., melting point of 168.7 ° C., MFR = 30 g / min [230 ° C., load 2.16 kg, 10 minutes]) was charged into an extruder of a melt spinning apparatus, and heated at 280 ° C. The mixture was melt-kneaded and discharged from a 280 ° C. nozzle (0.4 mmφ, 24 holes) at a discharge rate of 34 g / min (1.4 g / min per hole). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of this undrawn yarn was 1.06 × 10 ⁻³ , and the ratio of the crystal structure was 40.1% by mass. The maximum breaking draw ratio at 135 ° C. of the undrawn yarn was 11.2 times. When stretched at a preheating temperature of 85 ° C. and a hot plate temperature of 135 ° C. at a rate of 300 m / min at 0.7 times the maximum breaking draw ratio, the strength of the obtained polypropylene fiber was 6.5 cN / as shown in Table 1. dtex, which was lower than any of Examples 1 to 10 described above. This is presumably because although the birefringence value was low, the crystal structure was α-crystal and the MFR was extremely high, so that the required strength could not be obtained.

（比較例３）
ポリプロピレン樹脂（プライムポリマー社製Ｙ２０００ＧＶ、樹脂の融点１６９．４℃、ＭＦＲ＝１８ｇ／分［２３０℃、荷重２．１６ｋｇ、１０分］）を溶融紡糸装置の押出機に投入して、２２０℃で溶融混練し、２２０℃のノズル（０．３ｍｍφ、２０ホール）から３０ｇ／分の吐出量（１ホールあたり１．５ｇ／分）で吐出した。２０℃の冷風を当てて冷却固化したのち、油剤を付着して、室温で３００ｍ／分の引取り速度でボビンに巻き取って未延伸糸を得た。この未延伸糸の複屈折値は３．３２×１０^-3、結晶構造の割合は４２．４質量％だった。未延伸糸の１５５℃での最大破断延伸倍率は８．８倍だった。予備加熱温度８５℃、熱板温度１５５℃で最大破断延伸倍率の０．７倍で３００ｍ／分の速度で延伸したところ、得られたポリプロピレン繊維の強度は、表１に示すとおり６．５ｃＮ／ｄｔｅｘだった。これはＭＦＲは本発明の規定内であるが、紡糸温度が他の例と比べて低過ぎて複屈折値が大きくなり過ぎたため、得られたポリプロピレン繊維の強度は比較例２と同様の低い値になったものと考えられる。 (Comparative Example 3)
A polypropylene resin (Y2000GV, manufactured by Prime Polymer Co., Ltd., melting point of resin: 169.4 ° C., MFR = 18 g / min [230 ° C., load: 2.16 kg, 10 minutes]) is charged into an extruder of a melt spinning device, and is charged at 220 ° C. The mixture was melt-kneaded and discharged at a discharge rate of 30 g / min (1.5 g / min per hole) from a 220 ° C. nozzle (0.3 mmφ, 20 holes). After cooling and solidifying by applying a cold air of 20 ° C., an oil agent was adhered, and wound around a bobbin at room temperature at a take-up speed of 300 m / min to obtain an undrawn yarn. The birefringence value of this undrawn yarn was 3.32 × 10 ⁻³ , and the ratio of the crystal structure was 42.4% by mass. The maximum breaking draw ratio at 155 ° C. of the undrawn yarn was 8.8 times. When the film was drawn at a preheating temperature of 85 ° C. and a hot plate temperature of 155 ° C. at a rate of 300 m / min at 0.7 times the maximum breaking draw ratio, the strength of the obtained polypropylene fiber was 6.5 cN / as shown in Table 1. It was dtex. This is because the MFR is within the range of the present invention, but the spinning temperature was too low compared to the other examples and the birefringence value was too large, so that the strength of the obtained polypropylene fiber was as low as that of Comparative Example 2. It is thought that it became.

Claims

A polypropylene resin having a melt flow rate of 12 g / min or more and 25 g / min or less is melted and discharged from the discharge hole of a spinning nozzle at a temperature higher than the melting point of the resin by 80.6 ° C. or higher and 150 ° C. or lower. And a method for producing an undrawn polypropylene yarn having a crystal structure ratio of 30% by mass or less.

The method for producing a polypropylene undrawn yarn according to claim 1, wherein a take-up speed of the undrawn yarn is 200 m / min or more and 500 m / min or less.

The method for producing a polypropylene undrawn yarn according to claim 1 or 2, wherein a birefringence value of the undrawn yarn is 0.1 × 10 ⁻³ or more and 2.5 × 10 ⁻³ or less.

A method for producing a polypropylene fiber, comprising: drawing a polypropylene unstretched yarn produced by the method according to any one of claims 1 to 3 at 110 ° C or higher and 160 ° C or lower to obtain a polypropylene fiber.